Where do you think the prejudice against other species comes from in the adults living in the Mysterious Beyond? Even in later movies the different types of dinosaurs tend to migrate together according to their species. It was especially evident in the original movie, but it’s present in most of the sequels too. Have none of the leaf eating dinosaurs ever thought about joining up and helping each other outside of the Great Valley?

It’s not just Leaf Eaters either, if you look closely. Other than the Dil and Ichy pairing (which appears to be out of necessity) and the Red Claw, Screech, and Thud pairing (which may also be out of necessity), other than perhaps chance encounters (like movie VI), we have never seen a bunch of Sharpteeth work together with other types of Sharpteeth or live with other types of Sharpteeth. (Indeed, one wonders if Chomper in, the Lonely Dinosaur, was the first one to actually try it. If so, as you can see, it didn’t work well. Even that kid rejected him and had his parents chase Chomper off.)

As for your first question, I had a fanfic that actually tried to address it. This chapter is part of the fanfic, and is a crucial part of it. Ironically, the fanfic is a LBT three-part FINALE but it does cover the original storyline too.

Several days after Littlefoot hatched, he asked his mother “Mother where is Dad?”
“Littlefoot, I do not know.” she replied. She had no idea if Bron was even still alive. He had gone to look for a better place for them to live. He, unlike her, didn’t believe that the Great Valley was even real. Hence, he had thought it a foolish quest and had a Plan B. Whatever he was looking for was sure taking some time.
Littlefoot was peeved about not having his father around, but he was happy enough with his mother and grandparents. None of them bothered to highlight to Littlefoot that he was a Longneck. They didn’t want him buying into the separation of the kinds. Still, as it was, they themselves didn’t dare try and break the status quo, for fear of being attacked by angry Leaf Eaters who lived it.
One day, Littlefoot was playing. His mother was nearby eating green food. It wasn’t the most plentiful in this famine. He noticed a strange looking green and orange creature. It came up to him. He naively licked it. It then opened its mouth, revealed fangs. The Slithering Sharptooth (Dinalysia) then gave chase. Littlefoot bolted. He cried “Mama!” His mother Arianna, who had been eating leaves, spat them out in horror as she saw her son in danger.
Littlefoot ran into a dead end. He turned, horrified, as the creature came toward him. However, he then started to smile as he saw a huge shadow coming. The Slithering Sharptooth didn’t see it though. Before the creature could attack. it was stomped on by Arianna, then grabbed in her mouth and hurled into the air and out of sight. Littlefoot was happy. His mother licked him with her tongue. He was glad that she was around to save him from the dangers of the world.
Of all the dinosaurs that would ever influence Littlefoot, Arianna was, without a doubt, the most influential. Littlefoot spent a lot of time with her. She learned many Longneck stories from her father and told them to Littlefoot. He really loved them.
However, one day about five years after she had laid his egg, Littlefoot finally discovered the other Leaf Eater types. He’d found a Threehorn. The girl was arrogant, but her father was really belligerent. Feeling it was for the best, she separated him from the young orange Threehorn. Littlefoot has asked her why the kinds had always been apart. She said that it had always been that way and that there would be plenty of Longnecks for him to play with in the Great Valley. However, he still wasn’t satisfied.
“I have noticed two flaws with how we raise our young. We try and keep reality from them. When we do tell them about reality, we then tell them that there is nothing they can do to change it, which is even worse than keeping it from them.” sighed Arianna.
“Mother, I want to know why we have to be apart from the other kinds. You said that it has always been that way. Do you have any idea why, any at all?” asked the young Littlefoot. “And why are Sharpteeth so bad? Grandpa says that I must always be careful around them. Are there any good ones?” he asked. Arianna sighed.
“Littlefoot, there is a long tale about what happened about our kinds and about Sharpteeth and the other two kinds.” said Arianna.
“Tell me. I want to hear it!” said the five-year old Littlefoot.
“One day, the Bright Circle created the dinosaurs. They all had flat teeth. They lived together in harmony for a long time. However, there came a day when the Leaf Eaters became selfish. Some asked to have spikes on their tails. Others asked for horns. Some asked for clubs on their tails. Others asked for long tails. They all wanted to be able to outdo each other.” said Arianna.
“What?! I thought we got those to fight the Sharpteeth!” gasped Littlefoot.
“No, Littlefoot, we got those because we turned on each other. The Bright Circle wouldn’t give them this wicked wish, but the Bright Circle’s sister, the lesser Bright Circle, was jealous of her brother’s prominence and granted their request out of spite. They started to fight over food and over things. Eventually, they came to taking the lives of others in order to increase their own lots in life. They also tended to separate among their own kinds, snubbing the kinds of others.” Arianna said.
“How awful!” said Littlefoot.
“This continued for a while, the land being stained with blood. Finally, the Bright Circle could stand it no longer. Therefore, he created a creature to punish the Leaf Eaters for their acts of wickedness.
Out of the mountains he fashioned creatures with Sharp Teeth, claws on their hands and feet. Others could fly and yet others could swim. They could eat only meat. Being made of the mountains, they were very hard to beat and could easily take a beating that few Leaf Eaters could take. They came and attacked the Flatteeth, punishing the guilty. The Bright Circle had the Sharpteeth doomed to hunt the Leaf Eaters.” said Arianna.
“Wait, isn’t there some way out?” asked the young Longneck, who felt sorry for the Sharpteeth.
“Yes. Oh but it seems so unlikely.” replied Arianna with a sigh. “It was said that only a strong willingness to be friends between a Sharptooth and a Leaf Eater could get the Sharptooth to stay friends with the Leaf Eaters for life and not hunt the Leaf Eaters. Otherwise, the Sharptooth, no matter how hard he tried, would be doomed to hunt the Leaf Eaters.”
“I could be friends with one.” said young Littlefoot hopefully.
“Littlefoot, I think the day would come sooner that Leaf Eaters would work together.” said Arianna, shaking her head.
“If there were a nice one, could I befriend him?” asked Littlefoot, not to be deterred.
“I suppose, if it was for real, and not a trick.”Arianna answered.
“What about the Egg Stealers? How did they come about?” inquired Littlefoot.
“The Leaf Eaters had learned their lesson for a while. However, one day, they started to be cruel to their children. Many children, having had broken lives, continued the abuse on to their children.
Once more, the Bright Circle had had enough. The Bright Circle turned the child-abusing Leaf Eaters into Egg Stealers, where they would now prey upon the child of others in order to live and would steal the eggs of both Flatteeth and Sharpteeth. The Egg Stealers still could eat green if they chose, but only a friendship between a Leaf Eater and an Egg Stealer was said to be able to rid the Egg Stealer of the cruelty in his heart that naturally was there.” said Arianna.
“I could do that.” said Littlefoot.
“You are very brave my boy.” said Arianna.
“What about Bothteeth, Mother?” asked Littlefoot.
“After some time, there were some good Leaf Eaters who wanted to be able to survive during times of low green food. Thus, they begged the Bright Circle to be able to eat certain kinds of meat. As they had kind hearts, the Bright Circle consented. They became the Bothteeth.” said Arianna.
“So they became like Sharpteeth?” asked Littlefoot in concern.
“No, they do not eat the Leaf Eaters.” replied Arianna.
“Things continued as they were for a good while. Finally, some evil Leaf Eaters grew extremely greedy. They weren’t content to live as equals among their Leaf Eater brethren. They wanted power and strength to rule over the others.” continued Arianna.
“What happened, Mother?” asked Littlefoot in concern.
“They were not able to get the Bright Circle’s help in this. They saw how the Bothteeth could eat meat and wanted to have this ability. However, the Bright Circle knew that they were up to no good and so he refused.
So they go the help of the Bright Circle’s sister, the Lesser Circle instead. They demanded to have the abilities of Sharpteeth, so that they could hunt Leaf Eaters, Egg Stealers, and Sharpteeth alike. They wanted to reign over the world. They wanted the ability to take blows like Sharpteeth.
The Lesser Circle, jealous of the better spot her brother had, granted their request. They thus became an evil type of Bothtooth. Able to hunt their fellow dinosaurs and also eat leaves, they could survive in environments the other types couldn’t. Thus they became really strong and grew in power. Many of them could eat eggs as well. They soon sought out to rule the whole world.
The Bright Circle found out about this and was furious. He punished his sister by banishing her to be in the night sky, thus making her the Night Circle. This wicked type of Bothtooth was the Fanged Flattooth. The Fanged Flatteeth, unlike the other kinds, served the Night Circle. Thus the four kinds were created.” said Arianna, finishing her tale.
Littlefoot didn’t like the sound of the Fanged Flatteeth. If they were real, for he had never seen one (he’d seen Sharpteeth, Egg Stealers, and regular Bothteeth, and, just today, he’d seen another type of Leaf Eater. But never a Fanged Flattooth, he thought they were worse than Sharpteeth. Supposedly, Sharpteeth could only eat meat. If they had to kill to live, it wasn’t their fault. However, if the Fanged Flatteeth had WILLINGLY chose to kill, he didn’t have any sympathy with them. “Mother, are Fanged Flatteeth real? I’ve never seen one.” he asked.
“Oh Littlefoot, neither have I. I hope they aren’t.” she replied. “I hope it’s just the tale.”
“If they are real though, how can they be stopped? Is there a way to get the Leaf Eaters back together instead of always being apart?” he asked, concerned.
” There is a legend on the path to defeat the Fanged Flatteeth and reunite the Leaf Eaters. It says that only when a Leaf Eater is able to unite Leaf Eaters, Sharpteeth, Egg Stealers, and regular Bothteeth to his side as true friends can the Fanged Flatteeth meet their match.” Arianna said.
“I’ll be the one to do it.” he said boldly.
“Littlefoot, it is hard enough to bring Leaf Eaters together. To keep a Sharptooth friend past the time of Great Growing is a feat that would only be attempted by the noblest, bravest, kindest Leaf Eater ever to live.” said Arianna skeptically.
“I’m going to do it. I’ll do it all: other Leaf Eaters, Sharpteeth, Egg Stealers, and Bothteeth!” said young Littlefoot boldly.
“Littlefoot, you would be making a big dent in the status quo to do that.” sighed Arianna.
“What’s status-quo?” asked Littlefoot.
“It is what is now and it concerns those unwilling to change what has always been.” Arianna answered.
“Like the separation of the kinds?” Littlefoot asked.
“Precisely.” Arianna said.
“I don’t care. I’ll go against them, whatever it takes!” vowed Littlefoot.
“Then you will need to remain steadfast. Never give up on your dreams Littlefoot. Never let anybody talk you out of it.” she said. “Above all, you must value friendship. You must learn to work together with other kinds if you hope to reach your dream.”
“Don’t lose your way
With each passing day
You’ve come so far
Don’t throw it away
Live believing
Dreams are for weaving
Wonders are waiting to start
Live your story
Faith, hope and glory
Hold to the truth in your heart
If we hold on together
I know our dreams will never die
Dreams see us through to forever
Where clouds roll by
For you and I
Souls in the wind
Must learn how to bend
Seek out a star
Hold on to the end
Valley, mountain
There is a fountain
Washes our tears all away
Words are swaying
Someone is praying
Please let us come home to stay
If we hold on together
I know our dreams will never die
Dreams see us through to forever
Where clouds roll by
For you and I
When we are out there in the dark
We’ll dream about the sun
In the dark we’ll feel the light
Warm our hearts, everyone
If we hold on together
I know our dreams will never die
Dreams see us through to forever
As high as souls can fly
The clouds roll by
For you and I.” she sang.
Littlefoot liked the tune of the song. He really loved his mother and assumed that she would be there to help him reach his goal. However, as fate would have it, the Fanged Flatteeth that neither of them were sure existed would snatch her from him, forcing him to continue on his journey on the Circle of Life without her.